High current burn-in of solar cells
View Patent ↗A method of high reverse current burn-in of solar cells and a solar cell with a burned-in bypass diode are described herein. In one embodiment, high reverse current burn-in of a solar cell with a tunnel oxide layer induces low breakdown voltage in the solar cell. Soaking a solar cell at high current can also reduce the difference in voltage of defective and non-defective areas of the cell.
1. A method of improving efficiency of a solar cell, the method comprising:
applying, to a tunnel oxide layer of the solar cell, a reverse current which is higher than an operating current of the solar cell when the solar cell is reverse biased, wherein the applied reverse current has a magnitude of 5 amps or greater, and wherein the tunnel oxide layer includes a defective portion having a first breakdown voltage and a non-defective portion having a second breakdown voltage;
wherein the applied reverse current is to pass through the non-defective portion of the tunnel oxide layer of the solar cell;
wherein the magnitude of the applied reverse current is sufficient to physically degrade the non-defective portion of the tunnel oxide layer to decrease the second breakdown voltage of the non-defective portion.
2. The method of claim 1 , wherein the applied reverse current is higher than an operating current of the solar cell when the solar cell is forward biased.
3. The method of claim 1 , wherein the applied reverse current results in a current density that is higher than an operating current density of the solar cell when the solar cell is forward biased.
4. The method of claim 1 , wherein the applied reverse current results in a current density that is at least 30 mA/cm 2 .
5. The method of claim 1 , wherein the reverse current applied to the solar cell results in a current density that is 75% or greater than the operating current density of the solar cell when forward biased.
6. The method of claim 1 , wherein the non-defective portion of the tunnel oxide layer through which the reverse current is to pass has an area of 0.001% or less of the tunnel oxide layer of the solar cell.
7. The method of claim 1 , wherein applying the reverse current comprises applying the reverse current to the solar cell for a period of time sufficient to physically degrade the non-defective portion of the tunnel oxide layer, wherein the sufficient period of time is less than one minute.
8. A method of improving efficiency of a solar cell comprising:
physically degrading a non-defective portion of a tunnel oxide layer in the solar cell via application of a reverse current having a magnitude of 5 amps or greater to form a physically degraded region of the non-defective portion of the tunnel oxide layer of the solar cell and to decrease a breakdown voltage of the solar cell;
wherein current is to pass through the physically degraded region of the non-defective portion of the tunnel oxide layer of the solar cell when the solar cell is reverse biased.
9. The method of claim 8 , wherein physically degrading the non-defective portion of the tunnel oxide layer in the solar cell comprises physically degrading both a defective portion and the non-defective portion across the solar cell.
10. The method of claim 8 , wherein physically degrading the non-defective portion of the tunnel oxide layer in the solar cell comprises applying a reverse current to the solar cell, wherein the applied reverse current results in a current density that is 75% or greater than an operating current density of the solar cell when in forward bias.
11. The method of claim 8 , wherein physically degrading the non-defective portion of the tunnel oxide layer in the solar cell comprises applying a reverse current to the solar cell, wherein the applied reverse current results in a current density of at least 30 mA/cm 2 .
12. The method of claim 8 , wherein physically degrading the non-defective portion of the tunnel oxide layer comprises reducing a voltage drop across the tunnel oxide layer when the solar cell is reverse biased.